Cameron knows white people have to see themselves in a character.
And if we're being charitable, focusing on the actions of the white imperialist could be read as "here's what a white imperialist can do instead of going along with it, ineffectively resigning in protest/going AWOL, marching against it at home, boycotting products made with unobtanium, etc." Pointing out that using your knowledge of the imperial machine to help destroy it is a good message, even if a better movie would focus on a Na'vi Ho Chi Minh with Jake Sully as a supporting character.
And if we're being charitable, focusing on the actions of the white imperialist could be read as "here's what a white imperialist can do instead of going along with it, ineffectively resigning in protest/going AWOL, marching against it at home, boycotting products made with unobtanium, etc." Pointing out that using your knowledge of the imperial machine to help destroy it is a good message, even if a better movie would focus on a Na'vi Ho Chi Minh with Jake Sully as a supporting character.